hen a new model is opened or started the program by default adds 4 windows. Each window has a different view on the 3D hull. The area of the window on which the model is drawn is called a viewport. Zooming in or out on the viewport is done by pressing the left mouse button and moving the mouse up or down while keeping the left button pressed. Users having a mouse wheel may find it convenient to zoom in or out using their mouse wheel. Panning the viewport is done in a similar manner, only with the right mouse button must be pressed. Only when the viewport displays a perspective view, as in the image to the right, two scrollbars are visible. These can be used to rotate and tilt the model. Another way to rotate the model is keeping the middle mouse button (or mouse wheel) pressed while dragging the mouse, also only in a in a perspective view. Additional options for each viewport are accessible from the popup-menu which shows after the right button of the mouse has been pressed. Ilustration 8 2.2 Selecting items. Only items visible in the viewport can be selected and only if the viewport is in wireframe mode (shading is turned off). In order to select points or edges the controlnet can only be selected when the interior edges has to be turned on. Faces are turned on. For more information concerning visibility options the reader is referred to 11. Visibility options. It is important to keep in mind that selected faces, edges or points remain selected even when they are not visible in the viewport due to a change in the visibility options. To select an item, simply click on it with the mouse. Selected items can be recognized because they are drawn in yellow. If a point is selected, and the user clicks on a different point, this new point will be selected and the previous point will be deselected. Selecting multiple points however is possible by keeping the CTRL-key pressed while clicking on a new point. If the CTRL key is pressed while an edge is being selected, the program tries to trace the edge until a irregular point is encountered or an edge with a different crease-property. This way it is easy to select an entire row of edges (edgeloop) such as for example the sheerline or a hard chine. Faces also can be CTRL-selected. In that case all the faces belonging to the same layer and connected to the selected one are also selected or deselected. Faces that are isolated from the selected face because they are totally surrounded by crease edges are not included. 2.3 Dragging control points. One of the most important options when it comes to modeling the hull is dragging points. In order to do this the controlnet must be turned on. Although it is possible to select points in a perspective view, the actual dragging of the point can only be done in the bodyplan view, profile view or plan view. When dragging a controlpoint all information is updated realtime. This includes stations, buttocks, waterlines and diagonals. Especially when the precision of the model is set to a high value this updating might become slow since each intersection with the hull must be recalculated. If it becomes too slow, try using a lower precision. If it is still too slow, switch off some of these intersection curves since only visible items are recalculated, or try using less intersection curves.-13